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Shimla, Aug 3,
In a theoretical advancement published in the April–June 2024 edition of Physics Education, Shimla-based physicist Ajay Sharma has proposed a generalised version of Newton’s Third Law of Motion that introduces the role of an object’s shape and structural characteristics in determining the outcome of physical interactions. The journal is jointly published by the Himachal Pradesh Central University, Dharamshala, and the Himachal Pradesh Physics Teachers Association.
For over three centuries, Newton’s classical formulation — “for every action, there is an equal and opposite reaction” — has stood as one of the cornerstones of physics. However, Sharma argues that this statement, while conceptually powerful, lacks quantitative clarity in real-world conditions where interacting bodies are not identical in shape, size, or material. His paper, titled “Shape Dependent Form of Newton’s Third Law of Motion”, introduces a dimensionless coefficient ‘Q’ to represent these variables. According to Sharma’s formulation, the relationship becomes: Reaction = –Q × Action. The value of Q depends on factors such as shape asymmetry, composition, contact surface, and environmental conditions. When Q equals 1, the law reverts to Newton’s classical version.
In the study, Sharma presents conceptual experiments involving spherical and non-spherical bodies falling under identical conditions in a vacuum. Despite being equal in mass and composition, these bodies demonstrate varying rebounding behaviors, suggesting that Newton’s assumption of uniform reaction forces may not hold in such cases. This deviation, according to Sharma, highlights the limitations of applying Newton’s third law in complex, real-world scenarios without accounting for geometrical and structural influences.
Further, the paper makes a case for revisiting widely used equations in mechanics and propulsion physics, including those involving elastic collisions and the Tsiolkovsky rocket equation. Sharma notes that these classical equations assume idealised bodies and symmetrical forces, overlooking the role of shape and material interplay. The generalised approach he proposes may lead to improved accuracy in fields such as aerospace dynamics, particle mechanics, and robotic systems where interaction forces are crucial.
The study does not aim to negate Newton’s third law but rather to enhance its applicability through a more nuanced lens. Sharma, affiliated with the Fundamental Physics Society, supports his thesis with international references, including research from the American Association of Physics Teachers. He calls for experimental physics to validate and quantify the Q-factor across different scenarios, stating that this expanded model could bring classical mechanics closer to modern experimental realities.
“This work builds upon Newton’s foundations with a logical generalisation suited to today’s scientific understanding,” Sharma concludes in the paper, urging the global physics community to test and refine the proposed equation. If proven experimentally, the generalised form could influence how future engineers and scientists approach motion, impact, and force in complex systems.
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